Areas converted to lawns in Missouri can often harbor a suite of spring wildflowers, many of which never reach a height greater than 1 cm. Lawn wildflowers, most of them native to Europe, have adapted to living in these settings in America, and are well suited to living in consort with their primary disturbance factor: the lawn mower. These short little plants are abundant when found, with the spread of seed occurring with each mowing event. Lawns can actually be pretty diverse places--not like a high quality natural community, but a community nonetheless.
With the rampant spread of bush honeysuckle, many of our urban nature areas now lack even the flush of spring ephemerals which once grew in some of the most damaged natural communities. Little spots of woodlots that exist in neighborhoods--places where kids could build forts and play hide and seek--are wracked with bush honeysuckle. In urban areas like mine, nature is ceasing to exist in these areas once protected for "green space." It's not because of more and more development, but exotic species encroachment. With bush honeysuckle on the landscape, lawns in St. Louis can harbor greater species richness than the local trail system through the woods. It's sad that nature is so devastatingly damaged these days, so take biodiversity where you can find it.
Only a couple of the lawn plants are actually native to Missouri, but these little exotic weeds are seldom if ever found in Missouri's in tact natural communities. They remain loyal to lawns.
Jagged chickweed, Holosteum umbellatum: Also found on roadsides, Holosteum has a brief flowering period. In the 1963 Flora of Missouri, Steyermark reported that it was first documented in Missouri in 1950 in Washington Co. one mile south of Caledonia. Now established in southern and central Missouri, and north to St. Louis and Columbia. Introduced from Europe, jagged chickweed, according to Steyermark, is “like other spring annuals, often occuring in dense masses at the time of flowering. Eventually this species undoubtedly should spread over the greater portions of the state as detailed highway collecting will probably reveal."
Vernal whitlow grass, Draba verna : In 1963, this draba was found in 17 scattered counties. Introduced from Europe and Asia and today found in lawns, crop fields, fallow fields, pastures, roadsides, and disturbed areas throughout the state.
Little bluets, Houstonia minima: [Lousy photo, I know. I had better places to be than in the lawn next to the parking lot that day...] Blooming from January through April. Steyermark reports that it grows on "prairies, pastures, fallow fields, flood plains, rocky ledges and glades of sandstone, chert, granite. This is the commonest of the small bluets found in the spring, occurring in abundance and often making carpets of purple blue in grassy open places," like lawns.
Speedwells, namely Veronica polita: At Augusta Winery, I saw my first of the year blooming Veronica. Lots of Veronica species in Missouri, and while I didn't key this one out, I think it's V. polita. Note the low-growing habit of this plant; even a weedeater won't impact its flowering.
Here's a long list of some of the more common yard plants, not including the grasses that have also moved in to colonize yards that aren't treated with herbicide. Botany in your own front yard...
Yard flowers (not including many grasses)
Pimpernel Anagallis arvensis (tiny red flowers)
Lady’s thumb Polygonum persicaria
Jagged chickweed Holosteum umbellatum
Chickweed Stellaria media
Mouse-ear chickweed Cerastium species(as many as six species)
Small-flowered crowfoot Ranunculus abortivus
Early buttercup Ranunculus fascicularis (Ozarks primarily-cherty ground)
Whitlow grass Draba brachycarpa and D. verna
Peppergrass Lepidium virginianum
Low hop clover Trifolium campestre
Yellow wood sorrel Oxalis stricta
Milk spurge Chamaesyce supina (especially sidewalk and driveway cracks)
Johnny-jump-up Viola rafinesquii
Bindweed Convolvulus arvensis
Henbit Lamium amplexicaule
Purple henbit L. purpureum
Plantain Plantago lanceolata
Tiny bluets Houstonia minima
Dwarf fleabane Erigeron divaricatus
Common dandelion Taraxacum officinale
Bedstraw Galium virgatum
Neckweed Veronica peregrine
Speedwell V. polita
Thyme-leaved sandwort Arenaria serpyllifolia
Other natives in southern Ozarks
False garlic Nothoscordum bivalve (also found on dolomite glades)